using System;

​

struct Matrix4

{

    public int[,] Matrix;

    public Matrix4(int[,] matrix)

    {

        Matrix = matrix;

    }

​

    public static Matrix4 operator *(Matrix4 l, Matrix4 r)

    {

        int[,] nm = new int[4, 4];

        nm[0][0] = (l.Matrix[0][0] * r.Matrix[0][0]) + (l.Matrix[0][1] * r.Matrix[1][0]) + (l.Matrix[0][2] * r.Matrix[2][0]) + (l.Matrix[0][3] * r.Matrix[3][0]);

        nm[1][0] = (l.Matrix[1][0] * r.Matrix[0][0]) + (l.Matrix[1][1] * r.Matrix[1][0]) + (l.Matrix[1][2] * r.Matrix[2][0]) + (l.Matrix[1][3] * r.Matrix[3][0]);

        nm[2][0] = (l.Matrix[2][0] * r.Matrix[0][0]) + (l.Matrix[2][1] * r.Matrix[1][0]) + (l.Matrix[2][2] * r.Matrix[2][0]) + (l.Matrix[2][3] * r.Matrix[3][0]);

        nm[3][0] = (l.Matrix[3][0] * r.Matrix[0][0]) + (l.Matrix[3][1] * r.Matrix[1][0]) + (l.Matrix[3][2] * r.Matrix[2][0]) + (l.Matrix[3][3] * r.Matrix[3][0]);

​

        nm[0][1] = (l.Matrix[0][0] * r.Matrix[0][1]) + (l.Matrix[0][1] * r.Matrix[1][1]) + (l.Matrix[0][2] * r.Matrix[2][1]) + (l.Matrix[0][3] * r.Matrix[3][1]);

        nm[1][1] = (l.Matrix[1][0] * r.Matrix[0][1]) + (l.Matrix[1][1] * r.Matrix[1][1]) + (l.Matrix[1][2] * r.Matrix[2][1]) + (l.Matrix[1][3] * r.Matrix[3][1]);

        nm[2][1] = (l.Matrix[2][0] * r.Matrix[0][1]) + (l.Matrix[2][1] * r.Matrix[1][1]) + (l.Matrix[2][2] * r.Matrix[2][1]) + (l.Matrix[2][3] * r.Matrix[3][1]);

        nm[3][1] = (l.Matrix[3][0] * r.Matrix[0][1]) + (l.Matrix[3][1] * r.Matrix[1][1]) + (l.Matrix[3][2] * r.Matrix[2][1]) + (l.Matrix[3][3] * r.Matrix[3][1]);

​

        nm[0][2] = (l.Matrix[0][0] * r.Matrix[0][2]) + (l.Matrix[0][1] * r.Matrix[1][2]) + (l.Matrix[0][2] * r.Matrix[2][2]) + (l.Matrix[0][3] * r.Matrix[3][2]);

        nm[1][2] = (l.Matrix[1][0] * r.Matrix[0][2]) + (l.Matrix[1][1] * r.Matrix[1][2]) + (l.Matrix[1][2] * r.Matrix[2][2]) + (l.Matrix[1][3] * r.Matrix[3][2]);

        nm[2][2] = (l.Matrix[2][0] * r.Matrix[0][2]) + (l.Matrix[2][1] * r.Matrix[1][2]) + (l.Matrix[2][2] * r.Matrix[2][2]) + (l.Matrix[2][3] * r.Matrix[3][2]);

        nm[3][2] = (l.Matrix[3][0] * r.Matrix[0][2]) + (l.Matrix[3][1] * r.Matrix[1][2]) + (l.Matrix[3][2] * r.Matrix[2][2]) + (l.Matrix[3][3] * r.Matrix[3][2]);

​

        nm[0][3] = (l.Matrix[0][0] * r.Matrix[0][3]) + (l.Matrix[0][1] * r.Matrix[1][3]) + (l.Matrix[0][2] * r.Matrix[2][3]) + (l.Matrix[0][3] * r.Matrix[3][3]);

        nm[1][3] = (l.Matrix[1][0] * r.Matrix[0][3]) + (l.Matrix[1][1] * r.Matrix[1][3]) + (l.Matrix[1][2] * r.Matrix[2][3]) + (l.Matrix[1][3] * r.Matrix[3][3]);

        nm[2][3] = (l.Matrix[2][0] * r.Matrix[0][3]) + (l.Matrix[2][1] * r.Matrix[1][3]) + (l.Matrix[2][2] * r.Matrix[2][3]) + (l.Matrix[2][3] * r.Matrix[3][3]);

        nm[3][3] = (l.Matrix[3][0] * r.Matrix[0][3]) + (l.Matrix[3][1] * r.Matrix[1][3]) + (l.Matrix[3][2] * r.Matrix[2][3]) + (l.Matrix[3][3] * r.Matrix[3][3]);

        return new Matrix4(nm);

    }

}

public class Program

{

    public static void Main()

    {

        int[,] a = new int[4, 4] {

            {1, 2, 3, 4},

            {5, 6, 7, 8},

            {9, 10, 11, 12},

            {13, 14, 15, 16}

        };

        int[,] b  =new int[4, 4] {

            {17, 18, 19, 20},

            {21, 22, 23, 24},

            {25, 26, 27, 28},

            {29, 30, 31, 32}

        };

        Matrix4 Ma = new(a);

        Matrix4 Mb = new(b);

    }

}